Graphite and nanoclay flame retardant fabrics

ABSTRACT

A flame resistant textile fabric includes a coating having an expandable graphite, or a combination of an expandable graphite and a nanoclay, disposed on one or both of its first and second surfaces. The flame resistant textile fabrics may be used to make one or more components of a mattress, such as a filler cloth, or fabric fire barrier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Section 111(a) application relating to and claiming the benefit of U.S. Provisional Patent Application No. 62/473,774, filed on Mar. 20, 2017, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the field of flame-resistant fabrics, and, more specifically, to enhancements for improving the flame resistance of such fabrics and the flame resistance of items incorporating such fabrics.

BACKGROUND OF THE INVENTION

Each year, thousands of residential fires are caused in the United States by the ignition of mattresses and bedding, resulting in hundreds of deaths and hundreds of millions of dollars in property losses. Heightened awareness of fire prevention has led to the development of standards and regulations directed to reducing the likelihood that such fires will occur. One approach to reducing the likelihood of residential fires is to use flame-resistant fabrics as flame barriers in mattresses and bedding.

Conventional techniques for preparing flame-resistant fabrics include the use of inherently flame-resistant fibers, the chemical treatment of fibers or fabrics with flame retardant chemicals, and the incorporation of additives into the fiber matrix as the fiber is formed. Examples of inherently flame-resistant fibers include polyester fibers, polyaramid fibers, melamine fibers, and polybenzimidazole fibers. Chemical treatments include the impregnation or topical application of heat dissipaters (e.g., aluminum hydroxide or magnesium hydroxide) or free-radical quenchers (e.g., chemical compounds containing boron, phosphorous, nitrogen, antimony, or halogens). Additives that may be incorporated into the matrix of the fibers include some of the aforementioned chemical compounds, and silica as sodium silicate.

SUMMARY OF THE INVENTION

In an embodiment, a flame resistant textile fabric includes a first surface, a second surface opposite the first surface, and a coating disposed on at least one of the first and second surfaces, wherein the coating includes an expandable graphite. In an embodiment, the coating includes a nanoclay. In an embodiment, the expandable graphite present in the coating is in a range from about 5% to about 75% by weight, based on the total weight of solids in the coating. In an embodiment, a combination of the expandable graphite and the nanoclay present in the coating is in a range from about 5% to about 75% by weight, based on the total weight of solids in the coating. In an embodiment, the expandable graphite includes particles having particle size in a range of from about 297 microns (about 80 mesh) to about 37 microns (about 400 mesh). In an embodiment, the particles of the expandable graphite have a particle size of about 100 microns (about 140 mesh). In an embodiment, the particles of the expandable graphite have a particle size in a range of from 75 to 95 microns, with no more than ten percent (10%) of the particles of the expandable graphite having a particle size of 100 microns (about 140 mesh) or larger.

In an embodiment, the coating includes a latex binder. In an embodiment, the fabric is a woven flame resistant textile fabric. In an embodiment, the fabric is a woven flame resistant textile fabric.

BRIEF DESCRIPTION OF THE FIGURES

For a more complete understanding of the present invention, reference is made to the following detailed description of exemplary embodiments considered in conjunction with the accompanying drawings, in which:

FIG. 1 is a scanning electron microscopic image (SEM) of cross-sections of nanoclay-modified textile fibers according to an embodiment of the present invention;

FIG. 2 is a second SEM of another cross-section of a nanoclay-modified textile fiber according to the embodiment of FIG. 1;

FIG. 3 is a schematic process diagram of the burning behavior of a nanoclay-modified fiber of the same general type as the fiber of FIG. 1;

FIG. 4 is a schematic cross-sectional diagram of a mattress constructed in accordance with an embodiment of the present invention;

FIG. 5 is a schematic fragmentary view of a portion 5 of the mattress of FIG. 4;

FIG. 6 is a reproduction of a photograph of an apparatus used for a vertical test burn of a fabric sample;

FIG. 7 is a reproduction of a photograph of the apparatus of FIG. 6 with a fabric sample secured in a sample frame of the apparatus;

FIG. 8 is a reproduction of a photograph of a first view of a vertical test burn using the apparatus of FIG. 6; and

FIG. 9 is a reproduction of a photograph of a second view of the vertical test burn of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention includes textiles and textile fibers modified by incorporation of nanoclays (also referred to herein as “clay nanoparticles”) into the matrix of the fibers. As understood in a number of arts, the term “nanoclays” may refer to clays that are primarily formed from the layered aluminosilicate minerals known as phyllosilicates. Phyllosilicates delaminate in aqueous media to form platelets having thicknesses as small as 1 nm, and lateral dimensions (i.e., length and width) in ranges from tens of nanometers to hundreds of nanometers, or into the micron range. For the purpose of the present disclosure, the term “nanoclays” includes such phyllosilicates, as well as other mineral particles having at least one dimension that is in the range of about 1 nm to hundreds of nanometers. Exemplary nanoclays that may be used in embodiments of the present invention include, without limitation, bentonites, montmorillonites, hectorites, illites, and kaolinites. Organically-modified nanoclays may also be used in embodiments of the present invention.

One embodiment of the present invention includes a nanoclay-modified textile fiber. In such an embodiment, the textile fiber is an extruded fiber, such as viscose rayon. Referring to FIGS. 1 and 2, nanoclay-modified textile fibers 10 according to an embodiment of the present invention have nanoclay particles 12 distributed throughout the fiber matrix 14.

In a method of making such fibers, according to an embodiment of the present invention, the nanoclay may be mixed or dispersed into a flowable polymer or solution of polymeric precursors, which is then extruded to form the clay-modified fibers. Conventional extrusion methods or modifications of conventional extrusion methods may be used to form the fibers. In an embodiment of the present invention, the flowable polymer is cellulose of a type used to make viscose rayon. In an exemplary embodiment, the nanoclay content of the fiber is no more than 80% w/w. In an exemplary embodiment, the nanoclay content of the fiber is in the range of about 60% w/w to about 70% w/w. In an exemplary embodiment, the fiber is a viscose rayon fiber and the nanoclay is kaolin or kaolinite.

FIG. 3 is a schematic process diagram of the burning behavior of a nanoclay-modified fiber 16 according to an embodiment of the present invention. The fiber 16 comprises nanoclay particles 18 in a cellulosic matrix 20. As a conventional cellulosic fiber (not shown) burns, it generally forms a char and releases gaseous decomposition products. When the nanoclay-modified fiber 16 is ignited, the nanoclay particles 18 migrate from the degraded matrix 20 to the fiber surfaces 22, 24, forming barriers 26, 28 to mass and heat transport. Each of the nanoclay-filled barriers 26, 28 itself is non-combustible and provides structural reinforcement to the charred fiber 16.

Another embodiment of the present invention includes a woven or non-woven textile fabric modified by application of a nanoclay-filled coating material to the fabric. FIG. 4 illustrates an arrangement of fabrics used in a mattress 30 in a schematic cross-sectional view. The mattress 30 includes a non-fabric core 32, which may be of any known type used in mattresses in general. The core 32 is surrounded by mattress ticking 34, which may be of any known type, and a filler cloth 36 including a textile fabric according to an embodiment of the present invention. A fabric fire barrier 38 is provided between the ticking 34 and core 32. In mattresses according to embodiments of the present invention, one or both of the filler cloth 36 and the fabric fire barrier 38 are fire-resistant fabrics according to embodiments of the present invention. In an embodiment, the mattress 30 is a non-flip mattress. In other embodiments, the arrangement of the fabrics in the mattress of FIG. 4 and similarly-arranged mattresses according to embodiments of the present invention may be readily adapted to reversible mattresses (not shown) in arrangements understood in the prior art. In an embodiment, the filler cloth 36 or the fabric fire barrier 38, such as those shown in FIGS. 4 and 5, or discussed elsewhere herein, may be used in other household furnishings (e.g., without limitation, mattress foundations or upholstered furniture) in arrangements known in the art.

FIG. 5 is a detail of the filler cloth 36 shown in FIG. 4, which is an embodiment of the fire-resistant fabrics of the present invention. The filler cloth 36 includes a textile substrate 40, and upper and lower coatings 42, 44, each of which extends along a respective surface of the textile substrate 40 and is integrated with the textile substrate 40. In embodiments of the present invention, the upper coating 42 and/or the lower coating 44 each extends along a respective surface of the textile substrate 40 and is integrated with the textile substrate 40. The filler cloth 36 is an exemplary embodiment of the flame-retardant fabrics of the present invention, which also include fire barriers, such as the fire barrier 38, and other coated flame-retardant fabrics.

In embodiments of the present invention, the textile substrate 40 includes a woven or non-woven textile containing at least cellulosic fibers (not shown). The cellulosic fibers may be fire-resistant cellulosic fibers, such as fire-resistant rayon (e.g., viscose) fibers, or non-fire-resistant cellulosic fibers. Fire-resistant nanoclay-modified fibers according to embodiments of the present invention are one of the types of fire-resistant fibers that may be used in the fire-resistant fabric of the present invention. Other types of fire-resistant fibers known in the art may also be used in the fire-resistant fabric of the present invention, including, without limitation, silica-modified fibers, chemically-treated fibers, polyester fibers, and thermoplastic polymeric fibers. In an embodiment, the textile substrate 40 is a blend of cellulosic fibers and thermoplastic polymeric fibers. In an embodiment, the cellulosic fibers constitute from about 60% to about 90% of the textile substrate 40, with the balance of the textile substrate being thermoplastic polymer fibers. In an embodiment, the textile substrate 40 is one of a 60/40 blend, a 65/35 blend, a 70/30 blend, a 75/25 blend, an 80/20 blend, an 85/25 blend, and a 90/10 blend of cellulosic fibers/thermoplastic fibers. The selection and manufacture of appropriate textile substrates for use in the present invention will be understood by those having ordinary skill in the art and possession of the present disclosure.

In embodiments of the present invention, coatings 42, 44 are latex coatings filled with nanoclay particles 46. In other embodiments of the present invention (not shown), one of the upper and lower coatings 42, 44 contains nanoclay particles 46 and the other does not. In yet other embodiments of the present invention, the filler cloth 36 has only an upper coating 42 or a lower coating 44.

In embodiments of the present invention, the coatings 42, 44 are applied to the textile substrate 40 as flowable coating materials. In embodiments of the present invention, such flowable coating materials include a carrier (e.g., water), a binder (e.g., a latex binder), and nanoclay particles. In some embodiments, the flowable coating materials further include a pigment. In some embodiments, the flowable coating materials further include auxiliary chemistries, such as wetting agents, surfactants, or pigment stabilizers. The selection and use of appropriate carriers, binders, pigments, and auxiliary chemistries will be understood by those having ordinary skill in the art and possession of the present disclosure.

In embodiments of the present invention, the flowable coating material has a composition in which the nanoclay is present in the coating material in the range of about 1% to about 30% by weight. In some embodiments, the nanoclay is present in the flowable coating material in range of about 10% to about 20% by weight. In an embodiment, the flowable coating materials include from about 10% to about 20% bentonite by weight in an aqueous suspension with about 5% acrylic latex as a binder. In an embodiment, the total solids content of such coating materials is approximately 50% w/w. The foregoing amounts of nanoclay, binder, and other solids may be varied without departing from the scope and spirit of the invention, as will be understood by those having ordinary skill in the art and possession of the present disclosure.

Continuing to refer to FIG. 5, in embodiments of the present invention, the flowable coating material is applied to the textile substrate 40 to form the coatings 42, 44. The flowable coating material may be applied to the textile substrate 40 by one or more of processes known in the art for applying flowable materials to sheets. Such methods include, without limitation, dip coating processes, spray coating processes, slot coating processes, and foam coating processes. Foam coating processes have been found to be particularly effective in applying the coating materials of the present invention to textiles. In an embodiment, the flowable coating material includes a liquid carrier, and the liquid carrier is driven off from the coatings 42, 44 after the flowable coating material is applied to the textile substrate.

In exemplary embodiments of the present invention, the nanoclay is present in the filler cloth 36 in an amount of about 20% by weight of the filler cloth 36. In exemplary embodiments of the present invention, the nanoclay is present in the filler cloth 36 in an amount in the range of about 0.005% about 20% by weight of the filler cloth 36. In exemplary embodiments of the present invention, the nanoclay is present in the filler cloth 36 in an amount in the range of about 0.005% to about 10% by weight of the filler cloth 36. In exemplary embodiments of the present invention, the nanoclay is present in the filler cloth 36 in an amount in the range of about 1% to about 3% by weight of the filler cloth 36, although, in some embodiments, the nanoclay is present in the filler cloth 36 in an amount of up to about 5% of the filler cloth 36. The amounts of coating material and/or nanoclay added to the textile may be varied without departing from the scope and spirit of the invention, as will be understood by those having ordinary skill in the art and possession of the present disclosure.

Further embodiments of coated filler cloths and other coated textile fabrics according to the present invention, as well as articles of manufacture incorporating such coated textile fabrics, are disclosed in U.S. patent application Ser. No. 14/273,123, filed on May 8, 2014, which is incorporated by reference herein in its entirety.

The following example is presented to demonstrate that nanoclay-modified fabrics of the present invention present superior reduction of thermal transfer and less shrinkage than coated fabrics without nanoclay.

Example

Samples of a non-woven textile were coated with one of two coatings (i.e., Coating 1 and Coating 2) by a foam coating process. Coating 1 was an aqueous suspension having roughly 50% solids by weight, including a pigment, about 5% acrylic latex by weight as a binder, and auxiliary chemistry. Coating 2 had the same composition as Coating 1, except that it included about 10% bentonite (CLOISITE NA+, BYK Additives, Inc., Gonzales, Tex.) by weight. The coatings were applied to a stitch-bonded, non-woven blend of silica-filled FR rayon fibers (65%) and polyester fibers (35%).

The thermal transfer and shrinkage of the coated fabrics were tested using a vertical-burn test. FIG. 6 is a photographic image of the test apparatus 48 used to conduct the vertical burn test. FIG. 7 is a photographic image of a test sample 50 of a fabric mounted on a sample frame 52 of the test apparatus 48 of FIG. 6. FIG. 8 is a view of a vertical burn test of the test sample 50, wherein the flame 54 is seen at the front side 56 of the test sample 50. FIG. 9 is a view of the vertical burn test of test sample 50 viewed from the back side 58 of the test sample 50. Referring to FIGS. 6-9 collectively, the test apparatus 48 also includes a gas jet 60 having an outlet 62 positioned near the bottom 64 of the sample frame 52, a non-contact infrared temperature sensor 66 for measuring the temperature at the back side 58 of the test sample 50 (i.e., the side of the test sample 50 opposite the flame 54), an infrared temperature display 68 for reporting the temperature measured by the temperature sensor 66, and a mass flow controller (not visible) for controlling the flow rate of propane gas through the gas jet 60. These and other components of the test stand will be recognized and understood from FIGS. 6-9 by those having ordinary skill in the art, since the test apparatus 48 is similar to apparatuses known in the industry for use in test burns.

The test burn procedure used is discussed herein. After preparing and calibrating the test apparatus 48, a fabric sample 50 measuring 12 inches by 12 inches is cut from a roll of coated fabric, and secured in the sample frame 52. Liquid propane gas is delivered to a flame 54 at the outlet 62 of the gas jet 60 at a rate of about 5.1 liters per minute. The front side 56 of the test sample 50 is exposed to the flame 54 for 50 seconds, while the temperature at the back side 58 of the test sample 50 is measured and recorded. At the end of the burn, the test sample is allowed to cool and is examined. The maximum recorded temperature is reported, as well as any excessive charring, glowing, flaming, or shrinkage that was observed.

The results of the tests performed on fabrics prepared with Coating 1 or Coating 2 are presented in Table 1, wherein:

-   -   “N” is the number of samples tested;     -   “weight” is the average weight of the samples, reported in         ounces per square yard (osy);     -   “thickness” is the average thickness of the samples, reported in         inches;     -   “thermal transfer” is the maximum temperature measured at the         back side of the test sample during the burn, reported in         degrees Fahrenheit; and     -   “thermal shrinkage” is the percent reduction of the length of         the sample.

TABLE 1 Thermal Thermal N Weight Thickness Transfer Shrinkage Coating 1 24 3.42 0.026 600 10-15% Coating 2 20 3.63 0.027 424 none

It can be seen from Table 1 that Coating 2 performed better than Coating 1 in the burn tests, reducing thermal transfer by 30% and the extent of shrinkage by 10-15%. In addition, the average weight of the fabric coated with Coating 2 was only 6% greater than the average weight of the fabric coated with Coating 1. The use of coatings having nanoclay coatings would thus reduce the rate of flame propagation and provide a flame barrier, while protecting the structural integrity of the coated fabric.

In further embodiments of the present invention, a textile substrate, such as the textile substrate 40 of the filler cloth 36 described above, is coated with an intumescent material that expands when heated to its activation temperature. In an embodiment, the upper and lower coatings 42, 44 include the expanded intumescent material. In another embodiment, one of the upper and lower coatings 42, 44 includes the expanded intumescent material. In an embodiment, the expanded intumescent material fills seams and openings that result from sewing or quilting textiles, or from attaching the textiles to frames. The expansion of the intumescent material also decreases the permeability of the textile, thereby blocking the flow of hot gases, and provides a thermally-insulating surface. In some embodiments, the intumescent material is applied to the textile (e.g., the textile substrate 40) such that it partially or completely fills the seams or openings, resulting in a more rapid and complete blocking of hot gases that would otherwise penetrate the textile.

In an embodiment, the intumescent material is expandable graphite. In an embodiment, the expandable graphite used as the intumescent material is treated with an acid (e.g., sulfuric acid, nitric acid, acetic acid, etc.), which permeates the layers of the graphite structure and, and causes the graphite to become expandable. The graphite forms a thick, thermally-insulating layer of carbon char when exposed to flame, heat, hot gases, or molten materials, and effectively blocks the progress of the flame. In an embodiment, the graphite expands up to 5 times its initial volume at its activation temperature. In an embodiment, the graphite expands up to 10 times its initial volume at its activation temperature. In an embodiment, the graphite expands up to 20 times its initial volume at its activation temperature. In an embodiment, the graphite expands up to 50 times its initial volume at its activation temperature. In an embodiment, the graphite expands up to 100 times its initial volume at its activation temperature. In an embodiment, the graphite expands up to 200 times its initial volume at its activation temperature.

In an embodiment of the present invention, the expandable graphite includes particles and is provided in a coating on a surface of the fabric. In an embodiment, the upper and lower coatings 42, 44 include the expandable graphite. In another embodiment, one of the upper and lower coatings 42, 44 includes the expandable graphite, such that one or both surfaces of the textile (e.g., the textile substrate 40) may have such a coating(s). In embodiments of the present invention wherein the graphite coated textile is used in an article of manufacture, such as a mattress, and, more particularly, the mattress 30, a coated surface of the textile faces outward from the article, so that the coated surface impinges a flame or hot gas. The textile substrates that may be used in embodiments of the present invention include those discussed above with respect to nanoclay-coated textiles.

In embodiments of the present invention, expandable graphite is applied to the textile substrate 40 in a flowable coating material. In some embodiments of the present invention, such a flowable coating material includes a carrier (e.g., water), a binder (e.g., a latex binder), and the expandable graphite particles. In some embodiments, the flowable coating material is a suspension containing the expandable graphite. In some embodiments, the flowable coating material also includes other materials or combinations of materials that are intumescent. In some embodiments, the flowable coating material includes both graphite and a nanoclay. In some embodiments, flame-retardant chemicals, such as those containing phosphorus, nitrogen, or boron, are included in the flowable coating material. In some embodiments, the flowable coating material further includes a pigment. In some embodiments, the flowable coating material further includes auxiliary chemistries, such as wetting agents, surfactants, or pigment stabilizers. The selection and use of appropriate carriers, binders, pigments, and auxiliary chemistries will be understood by those having ordinary skill in the art and possession of the present disclosure.

In embodiments of the present invention, the flowable coating material has a composition in which the expandable graphite, or combination of graphite and nanoclay, is present in the coating material in the range of about 5% to about 75% by weight based on the total weight of solids in the coating material. In some embodiments, the expandable graphite, or combination of graphite and nanoclay, is present in the flowable coating material in the range of about 15% to about 40% by weight based on the total weight solids in the coating material. In some embodiments, the binder is present in the flowable coating material in an amount up to about 50% by weight based on the total weight of solids in the coating material. In some embodiments, water and/or other carriers is present in the flowable coating material in an amount up to about 50% by weight based on the total weight of the coating material. The foregoing amounts of graphite, binder, and other solids may be varied without departing from the scope and spirit of the invention, as will be understood by those having ordinary skill in the art and possession of the present disclosure.

The optimum size of the graphite particles for any particular use is dependent on factors such as, but not necessarily limited to the following: the materials selected as the binder and carrier; the amount of graphite and other solids in the flowable coating material; the thickness of the coating on the textile; the desired appearance of the coated fabric; and the desired flexibility, feel, and wear properties of the coated textile.

In an embodiment, the size of the graphite particles is in the range of 80 mesh (about 297 microns) to 400 mesh (about 37 microns). In an embodiment, the desirability of preparing a stable flowable coating material, as well as the stability of the finished coating, is taken into account when selecting the particle size of the graphite. In an embodiment, the particle size of the expandable graphite is 100 microns or less. In other embodiments, the expandable graphite particle sizes are in a range of 75 to 95 microns (about 170 mesh), with no more than 10% of the expandable graphite particles having sizes of 100 microns (about 140 mesh) or larger. In the aforesaid range of examples, the graphite particles are mixed with an acrylic binder, and constitute from about 15% to about 40% of the total solids in the flowable coating material. Flowable coating materials according to the aforesaid range of embodiments are superior in response to flame, and do not adversely affect the aesthetic properties of the textile, such as softness and color.

As with the nanoclay coating materials discussed above, the graphite coating materials may be applied to the textile substrate by one or more of processes known in the art for applying flowable materials to sheets. Such methods include, without limitation, dip coating processes, spray coating processes, slot coating processes, and foam coating processes. In an embodiment, the graphite coating materials are applied to the textiles as pastes. In an embodiment, a flowable graphite coating material includes a liquid carrier, and the liquid carrier is driven off from the coating after the flowable coating material is applied to the textile substrate.

Further embodiments of coated filler cloths and other coated textile fabrics according to the present invention, as well as articles of manufacture incorporating such coated textile fabrics, are disclosed in U.S. Pat. No. 9,469,935, issued on Oct. 18, 2016, and U.S. patent application Ser. No. 14/877,611, filed on Oct. 7, 2015, both of which are incorporated by reference herein in their entireties.

It should be understood that the embodiments described herein are merely exemplary in nature and that a person skilled in the art may make many variations and modifications thereto without departing from the scope of the present invention. All such variations and modifications, including those discussed above, are intended to be included within the scope of the present invention. 

What is claimed is:
 1. A flame resistant textile fabric, comprising a first surface, a second surface opposite the first surface, and a coating disposed on at least one of the first and second surfaces, wherein the coating includes an expandable graphite.
 2. The flame resistant textile fabric of claim 1, wherein the coating includes a nanoclay.
 3. The flame resistant textile fabric of claim 1, wherein the expandable graphite present in the coating is in a range from about 5% to about 75% by weight, based on the total weight of solids in the coating.
 4. The flame resistant textile fabric of claim 2, wherein a combination of the expandable graphite and the nanoclay present in the coating is in a range from about 5% to about 75% by weight, based on the total weight of solids in the coating.
 5. The flame resistant textile fabric of claim 1, wherein the expandable graphite includes particle having a particle size in a range of from about 297 microns (about 80 mesh) to about 37 microns (about 400 mesh).
 6. The flame resistant textile fabric of claim 5, wherein the expandable graphite includes particle having a particle size of about 100 microns (about 140 mesh).
 7. The flame resistant textile fabric of claim 1, wherein the expandable graphite includes particles having a particle size in a range of from 75 to 95 microns, with no more than ten percent (10%) of the particles of the expandable graphite having a particle size of 100 microns (about 140 mesh) or larger.
 8. The flame resistant textile fabric of claim 7, wherein the coating includes a latex binder.
 9. The flame resistant textile fabric of claim 7, wherein the coating is derived from a flowable coating material which includes the expandable graphite is a suspension prior to deposition on the fabric.
 10. The flame resistant textile fabric of claim 7, wherein the fabric is a woven flame resistant textile fabric.
 11. The flame resistant textile fabric of claim 7, wherein the fabric is a nonwoven flame resistant textile fabric. 